* {
    margin: 0;
    padding: 0;
}

.cd-top {
    display: inline-block;
    height: 40px;
    width: 40px;
    position: fixed;
    bottom: 30px;
    right: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.05);
    /* image replacement properties */
    border-radius: 30%;
    overflow: hidden;
    text-indent: 100%;
    white-space: nowrap;
    background: rgb(248, 218, 162) url(../image/上箭头.png) no-repeat center 50%;
    visibility: hidden;
    opacity: 0;
    -webkit-transition: opacity .3s 0s, visibility 0s .3s;
    -moz-transition: opacity .3s 0s, visibility 0s .3s;
    transition: opacity .3s 0s, visibility 0s .3s;
}

.cd-top.cd-is-visible, .cd-top.cd-fade-out, .no-touch .cd-top:hover {
    -webkit-transition: opacity .3s 0s, visibility 0s 0s;
    -moz-transition: opacity .3s 0s, visibility 0s 0s;
    transition: opacity .3s 0s, visibility 0s 0s;
}

.cd-top.cd-is-visible {
    /* the button becomes visible */
    visibility: visible;
    opacity: 1;
}

.cd-top.cd-fade-out {
    /* if the user keeps scrolling down, the button is out of focus and becomes less visible */
    opacity: .5;
}

.no-touch .cd-top:hover {
    background-color: #e86256;
    opacity: 1;
}

@media only screen and (min-width: 768px) {
    .cd-top {
        right: 20px;
        bottom: 20px;
    }
}

@media only screen and (min-width: 1024px) {
    .cd-top {
        height: 60px;
        width: 60px;
        right: 30px;
        bottom: 120px;
    }
}

#login {
    position: absolute;
    width: auto;
    height: 30px;
    right: 40px;
    top: 5px;
    line-height: 30px;
}

#login div {
    float: left;
    width: 30px;
    height: 30px;
}

#login img {
    width: 100%;
    height: 100%;
    border-radius: 100%;
}

#login a {
    float: right;
    text-decoration: none;
    color: black;
    transition: color 0.3s;
}

#login a:hover {
    color: rgba(34, 151, 219, 0.473);
}

.top {
    width: 100%;
    min-height: 600px;
    background-attachment: fixed;
    background-image: url("../image/classroom.jpeg");
    background-size: cover;
    text-align: center;
    color: ghostwhite;
}

#title {
    padding-top: 180px;
    padding-bottom: 20px;
    font-size: 45px;
    font-weight: bold;
}

#desc {
    font-size: 25px;
}

.cardList {
    position: absolute;
    width: 1050px;
    height: 280px;
    bottom: -50px;
    left: 50%;
    margin-left: -525px;
    background-color: whitesmoke;
    border-radius: 5px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.3);
}

.card {
    background: rgba(245, 245, 245, 0.726);
    position: relative;
    height: 100%;
    width: 350px;
    float: left;
    box-shadow: 0 5px 10px rgba(0, 0, 0, 0.3);
    color: black;
    border-radius: 5px;
}

.card:hover {
    color: whitesmoke;
}

.card:hover .block {
    display: block;
}

#card1:hover {
    background: url("../image/card2.jpg");
    background-size: cover;
}

#card2:hover {
    background: url("../image/card1.jpeg");
    background-size: cover;
}

#card3:hover {
    background: url("../image/card3.jpg");
    background-size: cover;
}

.block {
    display: none;
    position: absolute;
    width: 100%;
    height: 100%;
    background: #474747;
    opacity: 0.15;
    z-index: 1;
}

.cardContent {
    position: relative;
    margin: 45px;
    z-index: 2;
}

.cardContent h2 {
    padding-bottom: 25px;
    font-weight: 500;
    font-size: 28px;
}

.cardContent p {
    margin-bottom: 5px;
    font-weight: 100;
}

.cardContent button {
    margin-top: 15px;
    width: 120px;
    height: 40px;
    background-color: rgb(82, 211, 170);
    border: none;
    border-radius: 5px;
    cursor: pointer;
}

.cardContent a {
    text-decoration: none;
    color: whitesmoke;
    font-size: 15px;
}

.desc {
    width: 100%;
    background-color: white;
}

.container {
    width: 100%;
    padding-top: 20px;
    padding-bottom: 20px;
    height: 420px;
    float: left;
}

.picture {
    float: left;
    width: 60%;
    height: 100%;
    margin: 30px 60px;
}

.picture img {
    width: 100%;
    height: 100%;
}

.content {
    height: 100%;
    width: 300px;
    float: left;
    margin-top: 180px;
}

.content h1 {
    color: rgb(136, 218, 136);
    margin-bottom: 15px;
}

#login .tipBox {
    display: none;
    position: absolute;
    top: 30px;
    left: 20px;
    width: 80px;
}

#login ul {
    background-color: rgb(106, 150, 151);
    border-radius: 5px;
    opacity: 0.9;
}

#login li {
    list-style: none;
    text-align: center;
}

#login li a {
    float: none;
}

#login li a:hover {
    color: white;
}